Influence of Fault Roughness on Earthquake Rupture Parameters Correlations

Geological observations show that fault surfaces are complex at both large scales (fault segmentation) and small scales (surface roughness). These geometric complexities strongly influence earthquake rupture behaviour, including slip, rupture speed, rise time, and peak slip velocity. Understanding how these rupture parameters are related to each other is essential for improving understanding of earthquake rupture physics and for developing synthetic rupture models that reproduce realistic dynamic behaviour within kinematic frameworks. Although earlier studies have examined these correlations, the effect of small-scale fault roughness is still not well understood. Therefore, this study focuses on understanding how fault roughness affects correlations among rupture parameters.

To address this problem, we use the dynamic rupture dataset of Mai et al. (2018), which includes twenty-one rupture models with different roughness realizations, roughness amplitudes, and hypocentre locations. Because dynamic slip-velocity functions have complex shapes, we simplify them by fitting the regularized Yoffe function proposed by Tinti et al. (2005). From these fits, we extract key kinematic parameters. We then examine correlations among eight parameters: slip, peak slip velocity, acceleration time, rise time, rupture speed, strike, dip, and rake.

Our results show that slip is positively correlated with rise time, but it does not show clear correlations with other rupture or geometry parameters. Peak slip velocity is negatively correlated with both acceleration time and rise time, and positively correlated with rupture speed. Importantly, as fault roughness increases, the correlation between peak slip velocity and rupture speed becomes weaker. Acceleration time is also negatively correlated with rupture speed, and this correlation also decreases with increasing fault roughness. In contrast, the geometry parameters strike and dip do not show significant correlations with any rupture parameters. Overall, fault roughness mainly affects the relationships between only two pairs of rupture parameters, whereas the correlations among other parameter pairs are not strongly affected.

Our findings provide important constraints for developing synthetic rupture models that can generate realistic high-frequency seismic radiation consistently with radiation of dynamic ruptures propagating on rough faults.